Groundwater samples collected at the planned relocation site for Tokyo's Tsukiji fish market have been found to contain toxic benzene at up to 100 times the government safety limit.

The warning was made by the Tokyo metropolitan government at a meeting of a panel of experts, where it was also reported that the survey conducted last month also revealed the presence of cyanide, The Japan Times reported.

Given these findings, the experts attending the meeting discussed measures to contain contaminated groundwater at the new site in Tokyo's Toyosu waterfront district, which was previously occupied by a gas production plant.

The measures intended to prevent the toxic groundwater from vaporizing in basement chambers involves covering the floors with either special sheet or concrete.

The plan to relocate the Tsukiji wholesale market, known for its daily fish auctions, by November 2016 has been stalled as Tokyo Governor Yuriko Koike decided to postpone the move amid concerns about soil and air pollution in the Toyosu area.

The relocation issue has drawn public attention as major buildings in the Toyosu market have been built atop hollow concrete chambers and not thick layers of soil, as recommended by pollution experts and as initially explained to the public, fueling concern about contamination.

The latest findings follow the results of a March survey, in which benzene at up to 100 times the government-set standard was detected in groundwater samples.